The present invention relates to a process to regulate the inner pressure of tanks and/or to establish defined flow conditions for gas currents in the head space of tanks.
When tanks are filled with gases or liquids, due to design or process-technological considerations, it is often necessary to ensure that the gas present in the head space of these tanks be specifically vented so that the inner pressure in the tank does not rise. This is the case, when gas is added to the tanks for example, for purposes of inertization, or when they are filled. The requirement to specifically vent gas from the head space is particularly crucial when the head space gas cannot be released directly into the atmosphere, but rather, has to be conveyed through pipelines or exhaust-gas cleaning systems which cause a loss of pressure. In order to overcome the pressure loss along the outlet line for the head space gas, it is then necessary to have an exhaust fan or pump. According to the state of the art, these aggregates are controlled by means of pressure measurement in the head space of the tank and, as a rule, this calls for quite complex measurement and control, since it is necessary to record even minute pressure increases. If commonly employed pressure gages are used to measure the pressure, the regulation of the pressure entails such a delay that--particularly when the outlet for the head space gas is separated from the head space by long lines--pressure increases occur which must be prevented. The use of more sensitive pressure-measuring devices involves high acquisition costs.